its probably just a pulled muscle, nothing to worry about, but STOP DOING EXERCISE YOU MOFO! it will go away soon, but just give it some time to rest, the best way of not over-working yourself, is always taking one day of the week in wich you dont do anything all day, for me its sunday, i just relax all day on sunday, it gives time for your muscles to un-stiffen, and your blood cells to re-generate :thumbsup: